package acme

import (
	"crypto"
	"crypto/rand"
	"crypto/rsa"
	"crypto/x509"

	"github.com/go-acme/lego/v4/certcrypto"
	"github.com/go-acme/lego/v4/registration"
	"github.com/traefik/traefik/log"
)

// Account is used to store lets encrypt registration info
type Account struct {
	Email        string
	Registration *registration.Resource
	PrivateKey   []byte
	KeyType      certcrypto.KeyType
}

const (
	// RegistrationURLPathV1Regexp is a regexp which match ACME registration URL in the V1 format
	RegistrationURLPathV1Regexp = `^.*/acme/reg/\d+$`
)

// NewAccount creates an account
func NewAccount(email string, keyTypeValue string) (*Account, error) {
	keyType := GetKeyType(keyTypeValue)

	// Create a user. New accounts need an email and private key to start
	privateKey, err := rsa.GenerateKey(rand.Reader, 4096)
	if err != nil {
		return nil, err
	}

	return &Account{
		Email:      email,
		PrivateKey: x509.MarshalPKCS1PrivateKey(privateKey),
		KeyType:    keyType,
	}, nil
}

// GetEmail returns email
func (a *Account) GetEmail() string {
	return a.Email
}

// GetRegistration returns lets encrypt registration resource
func (a *Account) GetRegistration() *registration.Resource {
	return a.Registration
}

// GetPrivateKey returns private key
func (a *Account) GetPrivateKey() crypto.PrivateKey {
	if privateKey, err := x509.ParsePKCS1PrivateKey(a.PrivateKey); err == nil {
		return privateKey
	}

	keySnippet := ""
	if len(a.PrivateKey) >= 16 {
		keySnippet = string(a.PrivateKey[:16])
	}

	log.Errorf("Cannot unmarshall private key beginning with %s", keySnippet)
	return nil
}

// GetKeyType used to determine which algo to used
func GetKeyType(value string) certcrypto.KeyType {
	switch value {
	case "EC256":
		return certcrypto.EC256
	case "EC384":
		return certcrypto.EC384
	case "RSA2048":
		return certcrypto.RSA2048
	case "RSA4096":
		return certcrypto.RSA4096
	case "RSA8192":
		return certcrypto.RSA8192
	case "":
		log.Infof("The key type is empty. Use default key type %v.", certcrypto.RSA4096)
		return certcrypto.RSA4096
	default:
		log.Infof("Unable to determine key type value %q. Use default key type %v.", value, certcrypto.RSA4096)
		return certcrypto.RSA4096
	}
}
